Method of making assemblies having stacked semiconductor chips

ABSTRACT

A method of manufacturing a plurality of semiconductor chip packages and the resulting chip package assemblies. The method includes providing a circuitized substrate having terminals and leads. A first microelectronic element is arranged with the substrate and contacts on the microelectronic element are connected to the substrate. A conductive member is placed on top of the first microelectronic element and is used to support a second microelectronic element. The second microelectronic element is arranged with the conductive member in a top and bottom position. The second microelectronic element is then also connected by leads from contacts on the second microelectronic element to pads and terminals on the circuitized substrate. The conductive member is then connected to a third pad or set of pads on the substrate. An encapsulant material may be deposited so as to encapsulate the leads and at least one surface of the microelectronic elements. The encapsulant material is then cured thereby defining a composite of chip assemblies which may be singulated into individual chip packages.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/611,390 filed Jul. 1, 2003, which application is based on U.S.Provisional Application No. 60/393,026 filed on Jul. 1, 2002, thedisclosure of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to stacked microelectronic assemblies, tomethods of forming such assemblies, and to components useful in suchassemblies.

Semiconductor chips are commonly provided as individual, prepackagedunits. A standard chip has a flat, rectangular body with a relativelyexpansive front face having contacts connected to the internal circuitryof the chip. Each individual chip is mounted in a package, which in turnis connected to a circuit panel, such as a printed circuit board, sothat the contacts of the chip are connected to conductors of the circuitpanel. In “flip-chip” designs, the front face of the chip faces thecircuit panel, and the contacts on the chip are connected to the circuitpanel by solder balls or other connecting elements. In many conventionaldesigns, the chip package occupies an area of the circuit panelconsiderably larger than the area of the chip itself.

As disclosed, for example, in certain embodiments of commonly assignedU.S. Pat. Nos. 5,148,265, 5,148,266 and 5,679,977, the disclosures ofwhich are hereby incorporated by reference herein, certain innovativemounting techniques offer compact assemblies with good reliability andtesting approaches. A package which can accommodate a single chip in anarea of the circuit panel equal to or slightly larger than the area ofthe chip itself is commonly referred to as a “chip-size package”.

The total area of a plurality of chips mounted on a circuit panel isalso a concern. Various proposals have been advanced for providingplural chips in a single package or module. It has been proposed topackage plural chips in a “stacked” arrangement, i.e., an arrangementwhere chips are placed one on top of another. In a stacked arrangement,several chips can be mounted in an area of the circuit panel that isless than the total area of the chips. Certain stacked chip arrangementsare disclosed, for example, in certain embodiments of the aforementioned'977 and '265 patents and in U.S. Pat. No. 5,347,159, the disclosures ofwhich are hereby incorporated by reference herein. U.S. Pat. No.4,941,033, also hereby incorporated by reference herein, discloses anarrangement in which chips are stacked one on top of another andinterconnected with one another by conductors on so-called “wiringfilms” associated with the chips.

Still further improvements in stacked chip assemblies, for incorporatingother elements within the assembly, would be desirable.

SUMMARY OF THE INVENTION

The present invention addresses these needs.

In a first aspect of the present invention, a microelectronic assemblycomprises a first microelectronic element having a first face with firstcontacts exposed at the first face. The first face faces in a firstdirection. A second microelectronic element has a first side with secondcontacts exposed at the first side. The first side faces in a seconddirection opposite to the first direction. The assembly includes asubstrate underlying the first microelectronic element and the secondmicroelectronic element. The substrate has first terminals, secondterminals, and at least one third terminal. The first contacts areconnected to the first terminals and the second contacts are connectedto the second terminals. A conductive member is disposed between thefirst microelectronic element and the second microelectronic element.The conductive member is connected to the at least one third terminal.An assembly according to this aspect desirably comprises a stackedarrangement of two microelectronic elements facing in oppositedirections and having a conductive member disposed therebetween. Themicroelectronic elements are connected to a substrate having terminalsfor forming connections with external elements, such as circuit boardsor other microelectronic elements. The conductive member may comprise aground plane or an electromagnetic interference shield.

In certain preferred embodiments, the first face of the firstmicroelectronic element faces the substrate and the first side of thesecond microelectronic element faces away from the substrate. The secondmicroelectronic element desirably overlies the first microelectronicelement. The substrate may have a first surface facing the firstmicroelectronic element and the second microelectronic element. Thesubstrate may also have a second surface facing in a direction oppositefrom the first surface. The features of the substrate desirably includepads exposed at the first surface of the substrate.

In certain preferred embodiments, the substrate includes first padsconnected to the first terminals. The first contacts may be connected tothe first pads. The first terminals are connected to the first pads andare desirably exposed at the second surface of the substrate. In certainpreferred embodiments, the first pads are connected to the firstcontacts by masses of bonding material. A dielectric material isdesirably disposed between the first face of the first microelectronicelement and the first surface of the substrate, and in-between themasses of bonding material. A dielectric material may also be disposedover the substrate, first microelectronic element and secondmicroelectronic element. Certain assemblies according to embodiments ofthe invention comprise a first microelectronic element attached to asubstrate in a flip-chip arrangement.

The substrate may include second pads exposed at the first surface ofthe substrate and connected to the second terminals. The second contactsof the second microelectronic element may be connected to the secondpads. In certain embodiments, the second contacts and second pads areconnected by wires. The second terminals are desirably exposed at thesecond surface of the substrate. The terminals desirably include viasextending through the substrate.

The substrate may include at least one third pad connected to the atleast one third terminal. The conductive element may be connected to theat least one third pad. The third terminal is desirably exposed at thesecond surface of the substrate. The conductive element may be connectedto the at least one third pad by at least one wire.

In certain preferred embodiments, the second pads and at least one thirdpad are disposed outwardly from the first microelectronic element.

In certain preferred embodiments, the first microelectronic element hasa second face facing oppositely from the first face and the secondmicroelectronic element has a second side facing oppositely from thefirst side. The conductive element is desirably disposed between thesecond face and the second side. The conductive element may be adheredto the second face and second side.

The substrate may comprise an edge. The first pads are exposed at thefirst surface of the substrate. The first contacts may be connected tothe first pads by a conductive element, such as a wire, extendingtransversely to the edge. The substrate may comprise an aperture and thefirst contacts may be connected to the first pads by a wire or otherconductive element, extending through the aperture.

In certain preferred embodiments, the conductive member has a firstwidth and the second microelectronic element has a second width lessthan the first width. The second microelectronic element overlies afirst portion of the conductive member and a second portion of theconductive member lies outwardly of the second microelectronic element.The substrate may include at least one pad exposed at the first surfaceof the substrate, the at least one pad being connected to the at leastone third terminal, and the conductive member may be connected to the atleast one pad at the second portion of the conductive member, outwardlyof the second microelectronic element.

In another aspect of the present invention, a method of making amicroelectronic assembly comprises providing a substrate having aplurality of pads, including first pads, second pads and at least onethird pad. The pads are exposed at a first surface of the substrate. Afirst microelectronic element is arranged with the substrate. The methodincludes connecting first contacts exposed on a first face of the firstmicroelectronic element to the first pads on the substrate.

A second microelectronic element and a conductive member are arrangedwith the substrate and first microelectronic element so that theconductive member is disposed between the first microelectronic elementand the second microelectronic element.

A first side of the second microelectronic element has second contactsexposed thereat. The second contacts are connected to the second padsand the conductive member is connected to the at least one third pad.Methods according to this aspect of the present invention provide amethod of making a stacked microelectronic assembly having a conductivemember disposed in the space between a first microelectronic element anda second microelectronic element. Methods according to embodiments ofthe present invention provide a method for forming electromagneticshielding or a ground plane between microelectronic elements in astacked electronic assembly. The assembly may comprise furthermicroelectronic elements. The conductive member may comprise a plate ofelectrically conductive material. The conductive member may comprise analuminum plate.

In certain preferred embodiments, the conductive member is connected tothe first microelectronic element and the second microelectronic elementis connected to the conductive member. In certain preferred embodiments,the conductive member is connected to the at least one third pad beforethe second contacts are connected to the second pads. The first face ofthe first microelectronic element may face the first surface of thesubstrate and the first contacts may be connected before the secondcontacts and the conductive member.

In certain preferred embodiments, the step of connecting the firstcontacts to the first pads includes disposing masses of bonding materialbetween first contacts and the first pads. The step of connecting thefirst contacts to the first pads may include attaching wires to thefirst contacts and the first pads.

In certain preferred embodiments, the first microelectronic element hasa second face facing in a direction opposite to the first face. The stepof connecting the conductive member may include applying adhesive to thesecond face and attaching the conductive member to the second face. Anadhesive may be applied to the conductive member and a second side ofthe second microelectronic element is attached to the conductive member.The second side of the microelectronic element faces in a directionopposite to the first side. The adhesive may be cured after the step ofconnecting the second microelectronic element to the conductive member.Methods according to certain embodiments of the present inventioninclude a conductive member for shielding or ground connection that isdisposed between two microelectronic elements facing in oppositedirections.

The step of connecting the second contacts to the second pads mayinclude attaching wires to the second contacts and the second pads. Theconductive member may be connected to the at least one third pad byattaching wires to the conductive member and the third pad. The thirdpad may be arranged for connection with a ground or voltage source.

A flowable material is desirably introduced so as to surround at leastthe second contacts, second pads and third pads. A flowable material isdesirably introduced between the first face of the first microelectronicelement and the first surface of the substrate so as to surround thefirst pads and first contacts, after the step of connecting the firstcontacts to the first pads.

The conductive member may be wider than the second microelectronicelement and a portion of the conductive member disposed outwardly of thesecond microelectronic element may be connected to the at least onethird pad.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims and accompanying drawings where:

FIG. 1 is a cross-sectional view of the substrate with a plurality ofvias;

FIG. 2 is a cross-sectional view of the substrate with a firstmicroelectronic element overlying the substrate;

FIG. 3 is a cross-sectional view depicting the substrate and firstmicroelectronic element at a later stage in the method;

FIG. 4 is a cross-sectional view wherein an adhesive is overlying thefirst microelectronic element;

FIG. 5 is a cross-sectional view of a conductive element being placed ontop of the first microelectronic element;

FIG. 6 is a cross-sectional view depicting the assembly of FIG. 5 at alater stage in the method;

FIG. 7 is a cross-sectional view of packages formed in the method ofFIGS. 1–6 with a second microelectronic element included overlying theassembly;

FIG. 8 is a cross-sectional view of an individual assembly formed in amethod in accordance with a further embodiment of the present invention;and

FIG. 9 is a cross-sectional view of an individual assembly formed in amethod in accordance with another embodiment of the invention.

DETAILED DESCRIPTION

An embodiment of the invention is shown in FIGS. 1–7. As shown in FIG.1, a substrate 10 having a first surface 12 and a second surface 16facing in a direction opposite from the first surface 12. The substratedesirably comprises a rigid or flexible sheet of dielectric material.The substrate 10 may comprise polyimide, other polymers, or otherdielectric materials. The substrate may comprise FR4 or a circuit boardmaterial. The substrate includes a plurality of vias 20 extending fromthe first surface 12 to the second surface 16 and pads 22 aligned withthe vias 20. The pads 22 include first pads 22 a, second pads 22 b andthird pads 22 c, as will be discussed further below.

The pads in the embodiments shown in FIG. 1 include first pads 22 adisposed at a central region of the substrate 10 and second pads 22 band third pads 22 c disposed outwardly of the first pads. However, inother embodiments, the pads may have different arrangements with respectto one another.

A first microelectronic element 24 having a first face 26 facing in afirst direction 14 and having a plurality of contacts 27 exposed at thefirst face 26, is arranged with the substrate 10 so that the contacts 27face the first pads 22 a on the first surface 12. The firstmicroelectronic element 24 has a second face 28 that faces in the seconddirection 18, in a direction opposite from the first face 26. In theembodiment shown, the contacts 27 are connected to the first pads 22 aon the first surface 12. In certain preferred embodiments, the contacts27 are connected to first pads 22 a that are exposed at the secondsurface 16 of the substrate 10. In certain preferred embodiments, thefirst contacts 27 are bonded to the first pads 22 a in a “flip-chip”arrangement with the substrate 10, as shown in FIG. 2. For example,masses of bonding material 30 are disposed between the first pads 22 aand the first contacts 27. The masses of bonding material 30 are broughtto the reflow temperature of the bonding material and are then allowedto solidify so as to form a bond with the first contacts 27 and thefirst pads 22 a. The vias 20 desirably have conductive material 32disposed therein so as to line the vias 20 and form a connection withthe pads 22 a. The conductive material 32 is used in forming connectionswith external circuitry so that the substrate 10 interconnects themicroelectronic elements with external circuitry. The conductivematerial 32 may be deposited within the vias 20 before or after thefirst contacts 27 are connected to the first pads 22 a, but preferablybefore. As is known in the art, the conductive material 32 may bedeposited in the vias 20 utilizing methods such as sputtering or othermethods known in the art. A first dielectric material 35 is desirablyformed between the first face 26 and the first surface 12, as shown inFIG. 3. The first dielectric material 35 may be introduced between thefirst face 26 and first surface 12 by disposing a flowable materialtherebetween so that the flowable material penetrates between the massesof bonding material 30. The flowable material is then cured to form thefirst dielectric material 35. The first dielectric material 35 may beformed from a flowable, curable polymer.

A first layer of adhesive 37 is applied to the second face 28 of thefirst microelectronic element 24, as shown in FIG. 4. A first surface 38of a conductive member 40 is attached to the second face 28 utilizingthe adhesive 37, as shown in FIG. 5. A second layer of adhesive 42 isthen applied to the second surface 41 of the conductive member 40. Thesecond layer of adhesive 42 is then utilized to connect the secondmicroelectronic element 45 to the conductive member 40, as shown in FIG.6. The first layer of adhesive and the second layer of adhesive maycomprise a flowable material applied onto the second face 28 and thesecond surface 41 of the conductive member 40. The first layer ofadhesive 37 and second layer of adhesive 42 desirably comprise a thermaladhesive and the conductive member 40 may comprise a conductive plate,such as an aluminum plate. The conductive member 40 comprises anyelectrically conductive material.

As shown in FIG. 7, the second microelectronic element 45 has a firstside 48 with a plurality of second contacts 50 exposed at the first side48. The second microelectronic element 45 has a second side 52 facing inan opposite direction from the first side 48. The second microelectronicelement 45 is assembled with the conductive member 40 so that the secondside 52 abuts against the second layer of adhesive 42, attaching thesecond side 52 to the second surface 41 of the conductive member 40. Incertain preferred embodiments, the first layer of adhesive 37 and thesecond layer of adhesive 42 are cured by applying thermal or radiantenergy to the adhesive layers. The second layer of adhesive 42 andsecond microelectronic element 45 are desirably smaller in width thanthe conductive member 40 so that after the second microelectronicelement 45 is disposed on the conductive member 40, a first portion ofthe conductive member 40 is covered by the second microelectronicelement 45, while a second portion 54 of the conductive member 40 liesoutwardly of the second microelectronic element 45. This second portion54 is then connected to the third pads 22 c on the first surface 12 ofthe substrate 10. In certain preferred embodiments, wires 58 areattached at one end to third pads 22 c and then connected at a secondend to the second portion 54 of the conductive member 40. Thus, thesecond portion 54 lying outwardly of the second microelectronic element45 is utilized to connect to the substrate 10. However, in otherembodiments, an edge 56 of the conductive member may be used to connectto the third pads 22 c.

The second contacts 50 are connected to the second pads 22 b. In certainpreferred embodiments, wires 64 are connected at one end to the secondpads 22 b and then connected at another end to the second contacts 50.The wires may be formed by a process known in the art as wire bonding.However, in other embodiments, other conductive features are utilized toconnect the pads of the substrate 10 to the first contacts 27, theconductive member 40 and the second contacts 50. For example, any ofthese connections may be formed by masses of bonding material, such assolder, or by leads formed on the substrate 10, the firstmicroelectronic element 24 and/or second microelectronic element 45, orprovided separately.

The substrate 10 desirably has terminals 60 that are exposed at thesecond surface 16 of the substrate 10. The terminals may include solderballs 62, disposed in the vias 20. The solder balls 62 are desirablydeposited so as to connect with the conductive material 32 in the vias20. The terminals 60 b include first terminals 60 a that are connectedto the first pads 22 a, second terminals 60 b that are connected to thesecond pads 22 b and third terminals 60 c that are connected to thethird pads 22 c. The terminals 60 c are desirably arranged for formingthe desired connections for the second contacts 50. The first terminals60 a are desirably arranged for forming the desired connections for thefirst contacts 27. The third terminals 60 c are arranged to formconnections for the conductive member 40, such as connections to aground or voltage source, or other connections for electromagneticinterference shielding.

The substrate 10 may comprise one or more layers and may incorporateother features, such as traces or conductive planes. The pads andterminals carried by the substrate desirably comprise conductivematerials commonly used to form electrical connections and used inmaking microelectronic elements and microelectronic components, such ascopper and gold.

In other preferred embodiments, such as the embodiment shown in FIG. 8,the first microelectronic element 124 is assembled with the substrate110 and at least one aperture 111 is utilized to connect the firstcontacts 127 to first pads 122 a arranged on a surface of the substratethat faces away from the first microelectronic element 124. In certainpreferred embodiments, wires 158 are attached at one end to the firstcontacts 127 and then attached at another end to the first pads 122 aexposed on the second surface 116 of the substrate 110. A first face 126of the first microelectronic element 124 faces the substrate 110 and maybe attached to the substrate 110 using an adhesive. In certain preferredembodiments, a dielectric layer is formed between the first face 126 andsecond face 112. Such a dielectric layer may be formed as disclosed incertain embodiments of U.S. Pat. Nos. 5,679,977; 5,659,952; 5,706,174;and 6,169,328, the disclosures of which are hereby incorporated byreference herein.

In another embodiment of the invention, a substrate 210 having one ormore windows 211 and a plurality of leads 258 is assembled with thefirst microelectronic element 224. The first microelectronic element 224shown in FIG. 9 has a first face 226 with a plurality of first contacts227 exposed at a first face 226, in a central region of the first face.In other embodiments, contacts on the first microelectronic elementand/or second microelectronic element are arranged in one or more rowsin a central region, at the periphery or distributed across the face orside of the microelectronic element. The leads 258 and substrate 210 maybe formed as disclosed in certain embodiments of U.S. Pat. No.5,679,977, the disclosure of which is hereby incorporated by referenceherein.

In other preferred embodiments, more than two microelectronic elementsare incorporated within the assembly. For example, a dielectric pad maybe mounted on the first side 48 of the second microelectronic element 45shown in FIG. 7. Another conductive member 40 may be adhered to the padand a third microelectronic element may be adhered to the conductivemember. Alternatively, a third microelectronic element may be adhered tothe dielectric pad on the first side 48. A stack of microelectronicelements according to embodiments of the present invention may compriseany number of microelectronic elements.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A method of making a microelectronic assembly, comprising: a)providing a substrate having a plurality of pads, including first pads,second pads and third pads, exposed at a first surface of the substrate;b) arranging a first microelectronic element with the substrate andconnecting first contacts exposed on the first face to the first pads;c) connecting a conductive member to the first microelectronic element;d) connecting a second microelectronic element to the conductive member,a first side of the second microelectronic element having secondcontacts exposed thereat; e) connecting the second contacts to thesecond pads; and f) connecting the conductive member to the at least onethird pad, the conductive member being disposed between the firstmicroelectronic element and the second microelectronic element.
 2. Themethod of claim 1, wherein the conductive member is connected to the atleast one third pad before the second contacts are connected to thesecond pads.
 3. The method of claim 1, wherein the first face of thefirst microelectronic element faces the first surface of the substrateand the first contacts are connected before the second contacts and theconductive member.
 4. The method of claim 3, wherein the step ofconnecting the first contacts to the first pads includes disposingmasses of bonding material between the first contacts and the firstpads.
 5. The method of claim 1, wherein the step of connecting the firstcontacts to the first pads includes attaching wires to the firstcontacts and the first pads.
 6. The method of claim 1, wherein theconductive member is connected to the first microelectronic element andthe second microelectronic element by adhesive.
 7. The method of claim6, further comprising the step of curing the adhesive after the step ofconnecting the second microelectronic element to the conductive member.8. The method of claim 1, wherein the step of connecting the secondcontacts to the second pads includes attaching wires to the secondcontacts and the second pads.
 9. The method of claim 1, wherein the stepof connecting the conductive member to the third pads includes attachingwires to the conductive member and the third pads.
 10. The method ofclaim 9, wherein the third pads are connected to a ground or voltagesource.
 11. The method of claim 1, further comprising introducing aflowable material to the assembly so as to surround at least the secondcontacts, second pads, and third pads.
 12. The method of claim 1,further comprising introducing a flowable material between the firstface of the first microelectronic element and the first surface of thesubstrate so as to surround the first pads and the first contacts, afterthe step of connecting the first contacts to the first pads.
 13. Themethod of claim 1, wherein the conductive member comprises an aluminumplate.
 14. The method of claim 1, wherein the conductive member is widerthan the second microelectronic element and the conductive member isconnected to the third pads by attaching a wire to a portion of theconductive member disposed outwardly of the second microelectronicelement.